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The effect of temperature on the latent period is shown in the next two sets of records (figs. 80, 81). In fig. 80 we have three sets of records, taken with a 100 D.V. recorder at the three different temperatures of 23° C., 28° C., and 33° C. respectively, under a uniform stimulus-intensity of 2. These temperatures were maintained by means of the thermal chamber, heated electrically. From the lowest record at a temperature of 23° C. the latent period is seen to be .165 second. At 28° C. in the middle record, it is found

to be reduced to .125 second. And at 33° C. it becomes still further reduced to .065 second.

In fig. 81 these results are corroborated by records taken with a different specimen, under stimulus-intensity of 2, the vibration-frequency of recorder being 50 D.V. The three records are for temperatures of 24° C., 29° C., and 33° C respectively. The shortening of the latent period with rising temperature is also shown here in a very striking manner. The lowest of the records, taken at 24° C., gives us a latent period of .14 second. The next, at 29°C, shows a reduction to .102 second. And the last and highest, at 33° C., gives us a latent period of only .07 second.

The increase of vigour in the responsive movement under rising temperature is also very clearly apparent in the